^1,2Miguel Arribas Tiemblo,¹Pedro Rayo,¹María-Paz Martín-Redondo,¹Felipe Gómez
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009070]
¹Centro de Astrobiología (CAB), CSIC-INTA, Madrid, Spain
²Universidad de Alcalá de Henares (UAH), Madrid, Spain
Published by arrangement with John Wiley & Sons

Amino acids are an extremely heterogeneous group of biomolecules essential for life on Earth. Their biosignatures are expected to be easily degraded on the Martian surface as the absence of a thick atmosphere and a magnetosphere leads to most of the solar radiation directly reaching its surface. To determine the preservation of amino acids in the Martian regolith, and their detectability, we exposed protein-sourced and free amino acids to UV-B radiation. This was done while in contact with different particle size ranges of two Martian regolith simulants. Bulk analysis through High Performance Liquid Chromatography (HPLC) showed that UV-B radiation led to little damage across all samples, mainly targeting sensitive amino acids like tyrosine, histidine, tryptophan and methionine. The two Martian simulants were divided into five particle size ranges. Smaller particles (<0.045 mm) led to higher recoveries than bigger ones (>0.500 mm), likely through their high specific surface area. Raman spectroscopy offered localized surface information, which HPLC was unable to. One of the simulants (MMS-2) is rich in iron oxides like hematite, which likely prevented any detection by absorbing the excitation wavelength of the laser. Irradiation also led to widespread loss of signal of all amino acids. Overall, the limitations of both techniques were compensated by each another, which allowed for the precise characterization of the chemical alterations suffered by amino acids in these conditions.

^1,2Erbin Shi,²Alian Wang,³I-Ming Chou,¹Zongcheng Ling
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2024JE008867]
¹Shandong Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, School of Space Science and Physics, Institute of Space Sciences, Shandong University, Weihai, China
²Department of Earth & Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, MO, USA
³CAS Key Laboratory of Experimental Study Under Deep-Sea Extreme Conditions, Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya, China
Published by arrangement with John Wiley & Sons

Ferric sulfate minerals have been identified by orbital and landed missions at multiple locations on Mars and are the most common minerals in the Acid Mine Drainage (AMD) system on Earth. The occurrences and the speciation of ferric sulfates are very sensitive to variations in environmental conditions, such as temperature (T), relative humidity (RH%), redox potential (Eh), and potential of hydrogen ions (pH). In this study, two phase boundaries among kornelite, paracoquimbite, and ferricopiapite were experimentally derived in T–RH% space, using the well-established humidity buffer technique. The phase transformation and phase identification during experiments were determined by the gravimetric measurements and laser Raman spectroscopy, respectively. The two new phase boundaries clearly defined the edges of the stable fields of paracoquimbite that were ambiguously determined in a previous study. From the experimental data, we derived the entropy, enthalpy, and Gibbs free energy of the two reactions, and calculated the enthalpy changes and Gibbs free energy changes for each water of crystallization (either enter or escape from the structure) of these hydrous ferric sulfates. When compared with the same parameters of hydrous metal (Fe3+, Fe2+, Cu2+, Mg2+, Ni2+, Zn2+, Co2+, Mn2+, Cd2+, and Na+) sulfates derived by previous hydration/dehydration studies, we found a strong consistency, especially the Gibbs free energy changes. This finding implies the very consistent energetic barriers for the hydration/dehydration of those sulfates, post their first hydration/dehydration, regardless of their difference in cation and crystal structure.

^1,2Yun Chen et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2025JE009293]
¹National Key Laboratory of Aerospace Mechanism, Harbin Institute of Technology, Harbin, China
²Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
Published by arrangement with John Wiley & Sons

Micrometeoroid impacts play a key role in space weathering during the evolution of lunar regolith. The micro-cratering morphology and material transformation of common lunar phases are effective ways to understand the interaction between the space environment and matter, but there are few systematic studies. Micro-analysis is conducted on the microcraters in the Chang’e-5 lunar soil to evaluate the microscale impact effects. Here, our study reveals the different morphological characteristics and internal microstructure of microcraters across five typical components (pyroxene, olivine, plagioclase, ilmenite, and glass). The impact effects include planar defects like dislocation slip, amorphization, and the formation of np-Fe0 and vesicles. Key parameters, including the microcrater depth to diameter ratio and microcrater diameter to impactor diameter ratio, are calculated to quantify microcrater morphology. The formation process of microcraters is reproduced with the smoothed-particle hydrodynamic method. The results suggest that the microcraters retain transient characteristics, likely from low-speed micrometeoroids or secondary impact events. These microscale impacts exhibit lower intensity compared to microcraters from Apollo samples, indicating weak space weathering processes on young basalt. The exploratory work tries to provide a comprehensive summary of low-speed impact-induced microcraters in lunar soil and outlines the theoretical frameworks for understanding microscale impact processes.

¹Takaharu Saito, ¹Kengo Iwamoto, ²Shigekazu Yoneda, ³Seung-Gu Lee, ¹Hiroshi Hidaka
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2025.11.013]
¹Department of Earth and Planetary Sciences, Nagoya University, Nagoya 464-8601, Japan
²Department of Science and Engineering, National Museum of Nature and Science, Tsukuba 305-0005, Japan
³Geology and Space Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 34132, Republic of Korea
Copyright Elsevier

Neutron-capture reactions are fundamental processes driving isotopic variations among cosmic-ray-irradiated planetary materials. The energy spectra of neutrons interacting with these planetary materials provide insights into their cosmic-ray exposure conditions and enable quantitative estimates of neutron-induced isotopic shifts in elements of interest. In this study, we measured Yb and Hf isotopic compositions of Apollo15 deep drill core samples, which provide information on higher-energy neutrons compared with conventional neutron indicators of Sm, Gd, and Er. Furthermore, we developed a calculation method to reconstruct a neutron spectrum from isotopic shifts in Sm, Gd, Er, Yb and Hf. Applying the method to Apollo 15 samples revealed significant neutron spectrum variations in the lunar subsurface. The observed epithermal neutron spectrum variations likely reflect depth dependence of energy moderation processes of neutrons. A neutron spectrum at the lunar surface estimated from our data is enriched in lower-energy epithermal neutrons compared with those calculated from numerical calculations in previous studies. The depth-dependent spectrum variations observed in the Apollo 15 samples possibly affect correction calculations of neutron-capture effects for nuclides strongly influenced by epithermal neutrons, such as ¹⁷⁶Hf. This is important in the context of accurate interpretation of radiometric and isotopic studies of lunar samples, which often record significantly high neutron fluences due to long-time cosmic-ray exposure on the lunar surface.

¹Eloise E. Matthews,^1,2Auriol S. P. Rae,³Thomas Kenkmann,⁴Nicholas E. Timms,⁴Aaron J. Cavosie,¹Marian B. Holness
Meteoritica & Planetray Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70070]
¹Department of Earth Sciences, University of Cambridge, Cambridge, UK
²School of GeoSciences, University of Edinburgh, Edinburgh, UK
³Institute of Earth and Environmental Sciences—Geology, Albert-Ludwigs Universität Freiburg, Freiburg, Germany
⁴School of Earth and Planetary Sciences, Curtin University, Bentley, Western Australia, Australia
Published by arrangement with John Wiley & Sons

The majority of planetary impacts occur at oblique angles. Impact structures on Earth are commonly eroded or buried, rendering the identification of the direction and angle of impact—using methods such as asymmetries in ejecta distribution, surface topographic expression, central uplift structure, and geophysical anomalies—challenging. In this study, we investigate the potential of spatial asymmetries in shock metamorphism intensity to act as a quantitative constraint on the direction and angle of impact at the Gosses Bluff structure in Northern Territory, Australia. We measured the frequency of specific orientations of planar deformation features in quartz from nine samples around the central uplift and compared the spatial asymmetries in observed peak shock conditions with predictions from new three-dimensional numerical impact simulations of the formation of the Gosses Bluff structure. This comparison indicates formation by an impact along an approximately N→S trajectory at an angle of 52° ± 10°. The direction agrees with previous independent identification of structural asymmetry at the crater, although an attempt to constrain the impact angle has not been previously conducted. Alongside a trend of an increase in shock pressure recorded by down-range target rocks, we also observe a marked increase in shock metamorphism in the cross-range direction at Gosses Bluff. We attribute this pattern to the movement of faults in the central uplift during crater modification, displacing and dissecting the originally smooth distribution of shock metamorphism. This study provides new guidance for identifying and quantifying oblique impacts in the rock record, which is applicable to a large range of impact angles and crater sizes.

¹N. Topping et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70069]
¹School of Physics and Astronomy, University of Leicester, Leicester, UK
Published by arrangement with John Wiley & Sons

A correlative multi-technique approach, including electron microscopy and X-ray synchrotron work, has been used to obtain both structural and compositional information of a sulfur-bearing serpentine identified in several carbonaceous chondrites (Winchcombe CM2, Aguas Zarcas CM2, Ivuna CI, and Orgueil CI), and in Ryugu samples returned by the Hayabusa2 mission. S-K edge X-ray absorption spectroscopy was used to determine the oxidation state of sulfur in the serpentine in all samples except Ryugu. The abundance of this phase varies across these samples, with the largest amount in Winchcombe; ~12 vol% of phyllosilicates are identified as sulfur-bearing serpentine characterized by ~10 wt% SO3 equivalent. HRTEM studies reveal a d001-spacing range of 0.64–0.70 nm across all sulfur-bearing serpentine sites, averaging 0.68 nm, characteristic of serpentine. Sulfur-serpentine has variable S6+/ΣStotal values and different sulfur species dependent on specimen type, with CM sulfur-bearing serpentine having values of 0.1–0.2 and S2− as the dominant valency, and CIs having values of 0.9–1.0 with S6+ as the dominant valency. We suggest sulfur is structurally incorporated into serpentine as SH− partially replacing OH−, and trapped as SO42− ions, with an approximate mineral formula of (Mg Fe2+ Fe3+ Al)2-3(Si Al)2O5(OH)5-6(HS−)1-2(SO4)2−0.1-0.7. We conclude that much of the material identified in previous studies of carbonaceous chondrites as TCI-like or PCPs could be sulfur-bearing serpentine. The relatively high abundance of sulfur-bearing serpentine suggests that incorporation of sulfur into this phase was a significant part of the S-cycle in the early Solar System.

^1,2,3Hongyi Chen, ¹Jiankai Zhou, ^1,2Lanfang Xie, ^1,2Jinyu Zhang, ^1,2Zhipeng Xia
Icarus (in Press) Open Access Link to Article [https://doi.org/10.1016/j.icarus.2025.116873]
¹Institution of Meteorites and Planetary Materials Research, Key Laboratory of Planetary Geological Evolution of Guangxi Provincial Universities, Guilin University of Technology, Guilin 541006, China
²Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin 541006, China
³Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resources in Guangxi, Guilin University of Technology, Guilin 541004, China
Copyright Elsevier

The Mg-suite lithologies, particularly pink spinel-bearing rocks, provide critical insights into the Moon’s crust-mantle interactions and impact metamorphism. However, discrepancies persist between remote sensing interpretations and laboratory analyses regarding the petrological characteristics of pink spinel anorthosite (PSA) or pink spinel troctolite (PST). The unbrecciated lunar meteorite NWA 12279, identified as a pink spinel-bearing troctolitic anorthosite (PSTA), offers a pristine record with well-preserved igneous textures, minimal shock metamorphism (S1–S2), and low terrestrial weathering (W0–1) affecting its mafic minerals and spinels. Combined petrological, mineral chemical, Visible-Near Infrared (VNIR) spectroscopy, and Raman spectroscopic analyses reveal a homogeneous composition dominated by anorthite (81.8 ± 0.1 vol%, An = ~97.2), olivine (11.7 ± 1.3 vol%, Fo = ~76.8), augite-dominated pyroxene (4.75 ± 0.45 vol%, En = ~57.4), and Mg-spinel (0.96 ± 0.48 vol%, Mg# = ~82.4). Reflectance spectra from six selected profiles across the sample section show diagnostic absorptions at 1050 nm (olivine), 1950 nm (Mg-spinel), and 2300–2350 nm (high-Ca pyroxene), with spectral contrasts that correlate directly with the spatial distribution of spinel. Regions enriched in spinel display a notably stronger absorption depth at 1950 nm. Furthermore, we establish well-defined linear correlations (R2 ≥ 0.971) under low-shock conditions (<4 GPa) that enable robust in-situ composition prediction. These quantitative models—olivine Fo from Peak A (~820 cm−1; y = 3.050× – 2430), spinel Mg# from Peak B (~670 cm−1; y = 0.0461× + 50.82), and pyroxene En from Peaks C (~661 cm−1; y = 2.635× – 1701.5) and D (~1007 cm−1; y = 2.547× – 2522.4). These quantitative models help resolve orbital detection discrepancies for Mg-spinel-rich lithologies and provide essential ground truth for lunar mineralogy. Our findings demonstrate that even modest Mg-spinel abundances of ~1.0 vol% can produce detectable spectral signatures, challenging existing genetic models for lunar crustal evolution. This study underscores the value of Raman spectroscopy for future lunar missions and indicates a need to recalibrate orbital interpretations of Mg-suite lithologies.

¹Jintuan Wang et al. (>10)
Proceedings of the National Academy of Sciences of the USA 122, e2501614122 Open Access Link to Article [https://doi.org/10.1073/pnas.2501614122]
¹State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China

The impact history of the Moon provides the opportunity to better understand mass transfer in the Solar System. While Earth’s meteorite collection serves as a key reference for material flux in the Earth–Moon system, it suffers from profound biases arising from Earth’s orbital dynamics and atmospheric filtering. Systematic identification and classification of meteorites on the airless Moon thus provide additional critical constraints for reconstructing the primordial accretion history and impactor population of the inner Solar System. However, identifying impactors on the Moon remains challenging due to their vaporization upon colliding at high velocities with the lunar surface. In situ remote sensing has previously detected chondritic impactor materials in the South-Pole-Aitken (SPA) basin of the far side of the Moon. The first opportunity to measure materials from the SPA basin has come via the Chang’e-6 (CE-6) mission, which returned samples from the Apollo basin inside the SPA basin. In this study, we screened seven olivine-porphyritic clasts as potential impactor relics in regolith returned by the CE-6 mission. These clasts were identified, via textural characterization, olivine Fe–Mn–Zn systematics, and in-situ triple oxygen isotopes, as impact relics solidified from melted chondritic parent bodies. Intriguingly, the parent body of all the identified impactor relics in this study resemble CI-like chondrites, a volatile-rich meteorite group that is relatively rare in Earth’s meteorite collection. The detection and classification of these impactor relics impose significant constraints on the proportions of meteoritic materials in the Earth–Moon system and their potential contributions to water inventories on the lunar surface.

¹R. Keerthana, ¹R. Annadurai, ²K.N. Kusuma
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2025.116871]
¹Department of Civil Engineering, Faculty of Engineering and Technology, SRM Institute of Science and Technology, Kattankulathur 603 203, Tamil Nadu, India
²Department of Earth Sciences, Pondicherry University, Puducherry 605 014, India
Copyright Elsevier

This study investigates the morphology, mineralogy, and chronology of the Briggs crater (37 km diameter), situated west of the Oceanus Procellarum, employing high-resolution data from recent lunar missions. Lunar Reconnaissance Orbiter (LRO) images, Terrain Mapping Camera (TMC) Ortho images, and Digital Elevation Models (DEMs) from both the Chandrayaan-2 and Kaguya were employed to study the morphology of the crater. The morphological investigation identified distinct features in Briggs Crater, including a well-preserved crater rim, terraced walls, a convex floor indicative of subsurface uplift, an uplifted central peak, mounds, and prominent NE-SW and N-S trending concentric and radial fractures. Additionally, a fresh impact crater and localized slumping along the crater walls suggest ongoing surface modifications. Briggs Crater exhibits characteristics of a Class-2 Floor-Fractured Crater (FFC), including an uplifted floor and prominent concentric fractures, consistent with previously established classifications. The presence of radial and concentric fractures on the Briggs Crater floor suggests a combination of brittle and ductile deformation. Variations in fracture dimensions indicate differential stress distribution during floor uplift, likely influenced by subsurface magmatic intrusion or impact-induced processes. Integrated Band Depth (IBD) and Mineral indices-based color composite images were generated using M³ datasets to better understand mineralogy. These images enable the extraction of spectral signatures for mineralogical investigation and highlight the diversity of lithological composition. Spectral absorption analysis, IBD mapping, and mineral indices collectively confirm that the central peak exposes fresh High-Calcium Pyroxene (HCP) from deeper crustal levels, while the floor, rim, wall, and ejecta show weaker, mixed, and weathered pyroxene signatures. Integrating morphology and mineralogy with Crater Size-Frequency Distributions (CSFD)-based chronology, it has been suggested that Briggs Crater formed during the late Imbrian period (3.6 Ga). The N-S trending concentric fractures on the Briggs crater floor likely represent tectonic or magmatic activity that occurred between ~310 Ma and ~ 270 Ma during the Eratosthenian period, significantly after the initial crater formation.

¹Peter Mc Ardle,¹Rhian H. Jones,²Patricia L. Clay,¹Romain Tartèse,¹Ray Burgess,²Brian O’Driscoll,³Eric W.G. Hellebrand,¹Jonathan Fellowes,⁴Arthur Goodwin,¹Lewis Hughes
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70065]
¹Department of Earth and Environmental Sciences, The University of Manchester, Manchester, UK
²Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, Ontario, Canada
³Department of Earth Sciences, Utrecht University, Utrecht, Netherlands
⁴Ordnance Survey, Southampton, UK
Published by arrangement with John Wiley & Sons

Enstatite chondrites (ECs) formed on at least two parent bodies, EH and EL. After the accretion of the EC parent bodies, EC material was subjected to varying degrees of parent body thermal metamorphism (measured by petrologic types 3–6), due to heat released by radioactive isotope decay. Current schemes to determine the petrologic type of the ECs are qualitative and ambiguous, and many studies have included known or misclassified shock-melted ECs, which altogether have led to inconsistent classifications. In this study, we attempt to distinguish shock-melted ECs from other ECs so that we can assess the effects of thermal metamorphism alone. We identified a suite of geochemical parameters that allow us to classify rapidly cooled, quenched shock-melt ECs, including high-Fe (Mg,Mn,Fe)S monosulfide, high-Cr troilite, and high-Ni kamacite. We then screened out shock-melted samples. This then allowed us to establish a quantitative scheme to determine the petrologic type of an EC. This classification scheme is based on the petrography and geochemistry of glass, silicate minerals, sulfides, and metal. Specifically, for EH chondrites (which are similar but distinct from the EL group), among other parameters, the size and abundance of feldspar progressively increase from EH3 to EH6 (<13 μm, <8.5% modal% to >13 μm, 11.5 modal%), while the FeO content of enstatite changes from types 3–4 to types 5–6 (<0.45 wt% to >0.45 wt%). Additionally, we build on the work of others to propose a scheme that subdivides the EH3. Using the average Cr2O3 content of olivine, we divide the EH3 and EH4 chondrites into EH3Low (mean Cr2O3 > 0.25 wt%) and EH3High-EH4 subtypes (Cr2O3 < 0.25 wt%).